public class E3_6{
    public static void main(String a[]){
	double sum=0,item=1;
	int i=1,n=20;
	while(i<=n){
	   sum=sum+item;
	   i=i+1;
	   item=item*(1.0/i);
	}
	System.out.println("sum="+sum);
	}
}